When I send an item it has full address clearly marked, a full return address and is safely packed.

It also has a do not safe drop sticker, and if applicable tracking number and or registration.

If the item does not arrive I have completely filled my part of the deal.

If it is scanned as delivered and you still make a claim then I have every right to block you.

I have had customers who made multiple claims despite me having signatures for a registered item so Yes if you claim not to receive it my business can not afford to risk you.

If your feedback shows you have multiple comments about non delivery then yes I have every right to block you as my business can not afford the risk.

If you have a low score and suddenly items disappear then I have every right to block you.

If you will not pay for a safe form of postage then I have every right to block you.

If your name appears on my friends list of suss customers I have every right to block you.

If you are so worried about being blocked what is causing that? Because Ebay only protects buyers I must protect myself. Over the years I have sold a lot on Ebay and today it is very difficult to stay in the black with a significant increase in "suspicous" claims.

If I do block you, then you can always send a message and discuss it with me. Or do you prefer confrontation and hiding behind others.

If you do not wish to be open and honest I have every right to block you. Having been burnt quite a few times I have every right to protect myself and deal with people who are honest and open and want to buy my products.

And in answer to your first line.

Is there any rule that says I must offer the chance for people to rip me off more than once?

I have a saying "Do not perpetuate the problem"